Process for the preparation of SiOC-linked, linear polydimethylsiloxane-polyoxyalkylene block copolymers and their use

ABSTRACT

The invention relates to a process for the preparation of SiOC-linked, linear polydimethylsiloxane-polyoxyalkylene block copolymers having (AB) repeat units, via reaction of one or more polyetherdiols with a stoichiometric excess of α,ω-dihydropolydimethylsiloxanes and at least one tertiary amine as catalyst, which comprises, after completed reaction of the alcohol component, continuing the reaction in the presence of small amounts of water until no remaining ≡Si(H) groups are detectable by a gas-volumetric method.

This application claims benefit under 35 U.S.C. 119 (a) of German patentapplication DE 10 2006 061351.1, filed on 22 Dec. 2006.

Any foregoing applications, including German patent application DE 102006 061351.1, and all documents cited therein or during theirprosecution (“application cited documents”) and all documents cited orreferenced in the application cited documents, and all documents citedor referenced herein (“herein cited documents”), and all documents citedor referenced in herein cited documents, together with anymanufacturer's instructions, descriptions, product specifications, andproduct sheets for any products mentioned herein or in any documentincorporated by reference herein, are hereby incorporated herein byreference, and may be employed in the practice of the invention.

Citation or identification of any document in this application is not anadmission that such document is available as prior art to the presentinvention.

The invention relates to a process for the preparation of SiOC-linked,linear polydimethylsiloxane-polyoxyalkylene block copolymers having (AB)repeat units which comprise an average of ≧1 siloxane groups at theirends.

When flexible polyurethane foams are produced,polysiloxane-polyoxyalkylene block copolymers are added to the mixtureof the raw materials and have a variety of functions, inter aliapermitting formation of a uniform pore structure and stabilizing theresultant foam until the reaction is complete. However, not allpolysiloxane-polyoxyalkylene block copolymers are equally suitable. Tobe useful as polyurethane foam stabilizers, the polyoxyalkylene blocksand the polysiloxane block of the block copolymers have to be present ina balanced ratio, and the structure of the two blocks is also of greatimportance here. A wide variety of variables is available here both forthe polyoxyalkylene block and for the polysiloxane block, in creating afoam stabilizer of maximum effectiveness:

The polyoxyalkylene block can be composed of various oxyalkylene units,mainly oxyethylene units, oxypropylene units, and oxybutylene units. Theratio by weight of these units to one another can be varied here, as cantheir sequence, and also the molecular weight of the polyoxyalkyleneblock. Another important factor is the end group of the polyoxyalkyleneblock, which can be reactive (e.g. OH group) or inert (e.g. alkoxygroup) with respect to polyurethane formation. The polyoxyalkylene blockcan have linkage to the polysiloxane block via a hydrolytically stableC—Si bond or via a C—O—Si bond, which has lower hydrolytic stability.There can also be various polyoxyalkylene blocks bonded to thepolysiloxane block here.

The polysiloxane block can be varied with respect to the type andproportion of the Si units. The siloxane block can be straight-chain orbranched and can have varying molecular weight. The manner of bonding ofthe polyoxyalkylene blocks to the polysiloxane block can be terminaland/or pendent.

There is only limited possibility of prediction of effectiveness of apolysiloxane-polyoxyalkylene block copolymer as foam stabilizer. Theperson skilled in the art is therefore substantially forced to useempirical methods to test possible variations. In view of the large,almost infinite, number of possible variations, the discovery ofparticularly effective specific structural parameters and appropriateblock copolymers for the purposes of polyurethane production is anactivity which represents considerable technical progress and istherefore inventive.

There have been many previous descriptions ofpolysiloxane-polyoxyalkylene block copolymers having variouspolyoxyalkylene radicals in the average molecule. The followingspecifications are mentioned as representatives of the large number ofappropriate publications:

DE 10 2005 039 931.2 (US Patent Application Publication 2007-049717)describes a process for the preparation of SiOC-linked, linearpolydimethylsiloxane-polyoxyalkylene block copolymers having (AB) repeatunits. In said process, a small amount of a tertiary amine, e.g. fromthe group of the aromatic amines (pyridines, pyrimidines, pyridazine,pyrazine, quinoline, imidazole, etc.) and/or from the group of thecycloaliphatic amine bases (quinuclidine, diazabicyclo[2.2.2]octane,etc.), and here in particular 1,8-diazabicyclo[5.4.0]undec-7-ene, isadded at elevated temperatures to a reaction matrix composed ofaminosiloxane, polyoxyalkylenediol, and solvent, and thepolycondensation reaction is carried out by the general reaction≡SiNH₂+HOC≡→SiOC≡+NH₃ with liberation of ammonia until the desiredmolecular-weight increase has been achieved.

In U.S. Pat. No. 3,836,560 there is a previous description of thesecompounds, their use for the production of polyurethane foams, and alsoa process for their preparation. The content of said references ishereby incorporated by way of reference, and forms part of thedisclosure of the present application.

Said polyether siloxanes are valuable surfactant additives for theproduction of polyurethane foams, and in particular here theircell-opening action in ether foams or open-cell rigid foams isdesirable. A disadvantage in their industrial synthesis is that both thepreparation of the amine component, with its problem of salt production,and the coupling process itself are complicated, and some of thecompounds used in these operations are problematic and difficult tohandle under factory conditions.

It was therefore an object of the present invention to develop a simple,cost-effective process which can prepare (AB) block copolymers withimproved properties.

Surprisingly, a difference from the available prior art has now beenfound in that access to novel high-molecular-weight linear SiOC-linkedpolydimethylsiloxane-polyoxyalkylene block copolymers becomes availableif polyetherdiols are reacted with a stoichiometric excess ofα,ω-dihydropolydimethyl-siloxanes, in the presence of at least onetertiary amine as catalyst and small amounts of water.

This method gives, in a manner not foreseeable by the person skilled inthe art, structures which when used as stabilizers in the production ofpolyurethane foams (PU foams), in particular flexible PU foams, have adistinctly higher level of properties.

The invention therefore provides a process for the preparation ofSiOC-linked, linear polydimethylsiloxane-polyoxyalkylene blockcopolymers having (AB) repeat units, via reaction by methods known perse of polyetherdiols with a stoichiometric excess ofα,ω-dihydropolydimethylsiloxanes and one or more tertiary amines ascatalyst, which comprises, after completed reaction of the alcoholcomponent, continuing the reaction in the presence of small amounts ofwater until no remaining ≡Si(H) groups are detectable by agas-volumetric method.

The invention further provides for the use, as tertiary amine, of atleast one compound selected from the group consisting of the aromaticamines (pyridines, pyrimidines, pyridazine, pyrazine, quinoline,imidazole, etc.) and/or from the group of the cycloaliphatic amine bases(quinuclidine, diazabicyclo[2.2.2]octane, etc.),1,8-diazabicyclo[5.4.0]undec-7-ene and pyrimidine.

The invention further provides SiOC-linked, linearpolydimethylsiloxane-polyoxyalkylene block copolymers prepared by thisprocess.

The invention further provides the use of the compounds prepared by theinventive process as surfactant additives for production of polyurethaneether foams.

Further subject matters of the invention are characterized by theclaims.

It is noted that in this disclosure and particularly in the claimsand/or paragraphs, terms such as “comprises”, “comprised”, “comprising”and the like can have the meaning attributed to it in U.S. Patent law;e.g., they can mean “includes”, “included”, “including”, and the like;and that terms such as “consisting essentially of” and “consistsessentially of” have the meaning ascribed to them in U.S. Patent law,e.g., they allow for elements not explicitly recited, but excludeelements that are found in the prior art or that affect a basic or novelcharacteristic of the invention.

It is further noted that the invention does not intend to encompasswithin the scope of the invention any previously disclosed product,process of making the product or method of using the product, whichmeets the written description and enablement requirements of the USPTO(35 U.S.C. 112, first paragraph) or the EPO (Article 83 of the EPC),such that applicant(s) reserve the right and hereby disclose adisclaimer of any previously described product, method of making theproduct or process of using the product.

The siloxane blocks A of the copolymers mainly represent linear siloxanepolymers or chains having siloxane repeat units which can be representedby the molecular formula (—R₂SiO—)_(b).

The polyoxyalkylene block (B) of the linear block copolymers is anoxyalkylene polymer containing (—C_(n)H_((2n-m))R¹ _(m)O—)_(c)oxyalkylene repeat units.

The average molar mass of each siloxane block (A) is selected from theranges consisting of from about 650 to about 6500 g/mol, from about 800to about 1500 g/mol, and from about 1000 to about 1200 g/mol.

The number-average molar mass (Mn) of each polyoxyalkylene block of thecopolymers prepared in the invention is selected from the rangesconsisting of from about 600 to about 10 000 g/mol and from about 1000to about 5000 g/mol.

The size of the individual oxyalkylene units or siloxane blocks is notnecessarily uniform, but can vary as desired within the stated limits.

The individual polyoxyalkylene units are adducts composed of at leastone oxyalkylene monomer, selected from the group consisting of ethyleneoxide, propylene oxide, butylene oxide, and mixtures thereof. In oneembodiment of the invention, the adducts are mixed products composed ofat least two monomer units, e.g., ethylene oxide and propylene oxide.

The polyoxyalkylene blocks are in essence composed of oxyethylene unitsor oxypropylene units, e.g., mixed oxyethylene units and oxypropyleneunits with oxyethylene content of about 30 to about 70% by weight andoxypropylene content of from about 70 to about 30% by weight, based onthe total content of oxyalkylene units in the block.

The total content of siloxane block in the copolymer is is selected fromthe group consisting of from about 20 to about 50% by weight, from 25 toabout 40% by weight, and the content of the polyoxyalkylene blocks isfrom about 80 to about 50% by weight, and the number-average molar massMn of the block copolymer is selected from the group consisting of fromat least about 20 000 g/mol to about 160 000 g/mol, from about 25 000g/mol to about 100 000 g/mol, from about 30 000 g/mol to about 60 000g/mol, and from about 35 000 g/mol to about 50 000 g/mol. The averagemolar masses here are determined by a method based on the known methodsof GPC analysis.

For the purposes of the present invention, effective catalysts are oneor more tertiary amines selected from the group of the aromatic amines(pyridines, pyrimidines, pyridazine, pyrazine, quinoline, imidazole,etc.) and/or from the group of the cycloaliphatic amine bases(quinuclidine, diazabicyclo[2.2.2]octane, etc.), and here in particular1,8-diazabicyclo[5.4.0]undec-7-ene. A preferred catalyst combination inthe invention is composed of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)and pyrimidine. These compounds can be used in the form of a combinationfrom the start, or, for example, the reaction can be carried out withDBU as far as complete conversion of the OH groups and then continuedwith water and the pyrimidine as far as complete conversion of the SiHgroups.

Amounts usually used of the catalysts/catalyst combinations selectedfrom the group consisting of from about 0.01 to about 3.0 by weight, andfrom about 0.10 to about 2.30% by weight, based on the initial charge ofhydrosiloxane and polyether.

The molar ratio of α,ω-hydrosiloxanes to polyetherdiols is in the rangefrom about 1.00 to about 2.00, from about 1.25 to about 1.65, and fromabout 1.35 to about 1.55.

In one embodiment of the invention, the amount of water usedconcomitantly is the half-equivalent of theα,ω-dihydropolydimethylsiloxane excess used for formation of thecopolymer claimed in the invention. Amounts differing from this can beused, but do not provide any advantage in relation to the desired finalproducts, since either free Si—H groups or free water remain in thereaction mixture.

The inventive process is generally carried out via reaction ofpolyorganosiloxanes which contain —Si(H) units and which have thegeneral formula (II)

where:

-   R, independently of one another, are monovalent C₁-C₁₈ hydrocarbon    radicals, preferably alkyl, alkene, alkyne, cycloalkyl or aryl    radicals, which includes but is not limited to C₁-C₄ hydrocarbon    radicals, preferably alkyl radicals and methyl radicals, and-   b is selected from the range of from 8 to 80, from 10 to 50, and    from 10 to 25,    with at least one alcohol selected from the group of the    polyetherdiols with the general formula (III)    HO—(C_(n)H_((2n-m))R¹ _(m)O—)_(x)—H  (III)    where-   R¹, independently of one another, are C₁-C₄-alkyl radicals, (in one    embodiment of the invention, R¹ is methyl radicals and ethyl    radicals),-   n is from 2 to 4,-   m is 0 or 1, and-   x has a value selected from the group consisting of from 1 to 200,    from 10 to 100, and from 35 to 60,    where    the oxyalkylene segments —(C_(n)H_((2n-m))R¹ _(m)O—) can differ from    one another within an oxyalkylene ether radical, and the sequence of    the individual —(C_(n)H_((2n-m))R¹ _(m)O—) segments can also be as    desired, and this in particular encompasses block copolymers, random    polymers, and also combinations of these.

Polyetherdiols used in the invention include but are not limited tothose in which ethylene oxide (EO) and propylene oxide (PO) are presentin the form of copolymers. One embodiment of the polyetherdiols areEO/PO copolymers which have a block structure and which have EO contentof about 30 to about 70% by weight, based on the total content ofoxyalkylene units.

The analytical values for the compounds prepared in the inventiveprocess do not contradict the assumption that a difference from theprior art is achieved in obtaining access to high-molecular-weightlinear SiOC-linked polydimethylsiloxane-polyoxyalkylene block copolymershaving (AB) repeat units which have high-siloxane-content domains (X, Y)within their ends.

This method gives, in a manner not foreseeable by the person skilled inthe art, X-(AB)_(d)—Y structures which have high-siloxane-contentdomains (X, Y) within their ends.

The invention therefore further provides SiOC-linked, linear (AB)_(d)polydimethylsiloxane-polyoxyalkylene block copolymers of the generalformula (I)HO(R₂SiO)_(a)[(R₂SiO)_(b)(C_(n)H_((2n-m))R¹_(m)O)_(c)]_(d)(R₂SiO)_(e)H  (I)in which the substituents and indices are defined as follows

-   R, independently of one another, monovalent C₁-C₁₈, which includes    but is not limited to C₁-C₄ hydrocarbon radicals and methyl    radicals,-   R¹, independently of one another, methyl radicals and ethyl    radicals,-   a and e, are independently of one another, selected from the group    consisting of on average ≧1, preferably ≧5, and more preferably of    from ≧7 to ≦49, with the proviso that the sum (a+e)>1 preferably    with the proviso that the sum (a+e)≦50,-   b is selected from the ranges of from 8 to 80, from 10 to 50, and    from 10 to 25,-   c is ≧10, preferably ≧20, and more preferably of from ≧40 to ≦150,-   d is selected from the group consisting of ≧3 and ≦10, and ≧5 and    ≦8,-   m 0 or 1,-   n a number is selected from the group consisting of from 2 to 4, and    2 or 3.

The average molar mass of the siloxane blocks X(—R₂SiO—)a andY(—R₂SiO—)e, where R=—CH₃, is selected from the group consisting of from74 to 518 g/mol, from 148 to about 3000 g/mol, from 300 to about 2000g/mol, and from 500 to about 1200 g/mol.

One particularly sensitive and powerful method of evaluating thepresence of dimethylsiloxane blocks within the ends of the inventivecompounds is provided by the performance test in which the resultantcopolymer is introduced in the form of foam stabilizer into polyurethaneformulations for the production of, in particular, ether foams, oropen-cell rigid foams.

Inadequate content of siloxane blocks (X, Y) in the foam stabilizer isdiscernible as inadequate technical performance in the foaming process,examples being shrinkage or collapse.

The invention is further described by the following non-limitingexamples which further illustrate the invention, and are not intended,nor should they be interpreted to, limit the scope of the invention.

PREPARATION EXAMPLES

The SiOC-linked, linear polydimethylsiloxane-polyoxyalkylene blockcopolymers claimed in the inventive process can optionally be preparedwith or without use of a suitable solvent.

If high-molecular-weight SiOC-linked copolymers are desired, withattendant high viscosity, they can advantageously be prepared, with aview to their easy handling during and after synthesis, via the reactionof the respective polyetherdiol with the respective α,ω-hydrosiloxane ina suitable solvent.

Suitable solvents are alkanes, cycloalkanes, alkylaromatics, and thelike, and particular preference is given here to high-boiling solventswhose boiling points are >120° C.

The reactants, composed of at least one polyetherdiol and of one or moreα,ω-hydrosiloxanes, possibly with involvement of a solvent, can inprinciple together form an initial charge with intimate mixing atelevated temperature, and be reacted via addition of a sufficient amountof an inventive catalyst, or else can be introduced sequentially intothe reaction.

In one embodiment of the process, the polyetherdiol or the polyetherdiolmixture is treated in a high-boiling solvent at elevated temperaturefirst with a small amount of the concomitantly used inventive catalystand then, with good mixing, by a feed-controlled method, with theα,ω-hydrosiloxane or with a mixture composed of one or moreα,ω-hydrosiloxanes.

Excellent monitoring and control is possible when using this method toprepare the copolymers claimed in the invention, with liberation of gas.The individual components can also be added sequentially in order tocontrol the structure of the final product.

The molar ratio of α,ω-hydrosiloxanes to polyetherdiols is in the rangeselected from the group consisting of from about 1.00 to about 3.00,from about 1.0 to about 2.5, and from about 1.25 to about 1.70.

The amounts usually used of the catalysts are selected from the groupconsisting of from about 0.01 to about 3.0, and from about 0.10 to about2.30% by weight, based on the initial charge of hydrosiloxane andpolyether.

The reaction temperature for preparation of the inventive copolymersshould be elected from the group consisting of from about 110° C. toabout 160° C., and from about 120° C. to about 145° C.

Premature introduction of water into the reaction mixture, for examplevia water-containing starting materials or atmospheric moisture, is tobe substantially avoided in the inventive process. It has been foundthat although a reaction takes place, rising water content has anadverse effect on the desired favorable properties of the reactionproducts as additives in the production of polyurethane foams.

Example 1 Comparative Example

55.0 g of a polyoxyalkylenediol with average molar mass of 2800 g/moland ethylene oxide/propylene oxide ratio of about 1:1 are used asinitial charge together with 77.5 g of a linear alkylbenzene withboiling range of about 280 to 320° C., and 22.5 g of anα,ω-hydrosiloxane (average chain length N=15) in a stoichiometric ratio(OH group:≡SiH group=1:1), based on the polyether used, in a 500 mlfour-necked flask equipped with stirrer, internal thermometer, andreflux condenser with flexible gas-outlet tube. 0.1 g of1,8-diazabicyclo[5.4.0]undec-7-ene are then added to the mixture. SiHconversion determined by a gas-volumetric method is quantitative after 4h at 135° C.

Example 2

55.0 g of a polyoxyalkylenediol with average molar mass of 2800 g/moland ethylene oxide/propylene oxide ratio of about 1:1 are used asinitial charge together with 91.0 g of a linear alkylbenzene withboiling range of about 280 to 320° C., and 36.0 g of anα,ω-hydrosiloxane (average chain length N=15) in a 60% excess, based onthe polyether used, in a 500 ml four-necked flask equipped with stirrer,with precision glass gland, internal thermometer, and reflux condenserwith flexible gas-outlet tube. 0.1 g of1,8-diazabicyclo[5.4.0]undec-7-ene are then added to the mixture. SiHconversion determined by a gas-volumetric method is 63% after 8.5 h at135° C. Addition of 0.06% of H₂O, based on the entire mixture, completesthe reaction.

Example 3

55.0 g of a polyoxyalkylenediol with average molar mass of 2800 g/moland ethylene oxide/propylene oxide ratio of about 1:1 are used asinitial charge together with 88.2 g of a linear alkylbenzene withboiling range of about 280 to 320° C., and 33.2 g of anα,ω-hydrosiloxane (average chain length N=15), in a 50% excess, based onthe polyether used, in a 500 ml four-necked flask equipped with stirrer,with precision glass gland, internal thermometer, and reflux condenserwith flexible gas-outlet tube. 0.67 g of1,8-diazabicyclo[5.4.0]undec-7-ene are then added to the mixture. SiHconversion determined by a gas-volumetric method is 84% after 3 h at135° C. Addition of 0.34 g of pyrimidine and 0.03% of H₂O, based on theentire mixture, completes the reaction within 90 min.

Polydimethylsiloxane-polyoxyalkylene block copolymer obtained byinventive processes tested as foam stabilizer:

The performance test uses the typical formulation, constituted asfollows, for an ether foam:

Parts by weight Constituents of mixing specification 0.07 Kosmos ® 29(stannous 2-ethylhexanoate) from Goldschmidt GmbH 30 Polyol CP 3322(commercially available polyol) from DOW 70 Polyol CP 755 (commerciallyavailable polyol) from DOW 7 Polyol CP 1421 (commercially availablepolyol) from DOW 1.95 Water 0.2 Tegoamin ® BDE (bis(dimethylaminoethyl)ether solution) from Goldschmidt GmbH 0.3 Tegoamin ® 33(triethylenediamine solution) 0.2 Tegoamin ® DMEA (dimethylethanolaminesolution) 1.2 of foam stabilizer to be tested 40.3 tolylene diisocyanate(TDI 80) (corresponding to an index of 85).Testing of Foam Stabilizers:

The tin catalyst stannous 2-ethylhexanoate, the three polyols, thewater, and the three amine catalysts are used as initial charge in apaper cup and mixed for 60 s at 1000 rpm, using a disk stirrer. Theisocyanate is then added and incorporated for 7 s at 1500 rpm, using thesame stirrer. The mixture in the cup begins to foam here. It istherefore poured into a foaming box directly after stirring has ended.This has a basal area of 17×17 cm and a height of 30 cm. External PUfoam insulation of thickness 5 cm prevents excessively rapid cooling.The box has been designed with an internal plastics foil to permitsubsequent removal of the fully cured foam. Foam rises once the materialhas been poured into the foaming box. Ideally, gas pressure in the foamreduces once the maximum rise height has been reached, and the foam thenrelaxes slightly. The cell membrane of the foam bubbles opens there, andan open-pore cell structure is obtained in the foam. If stabilization isnot sufficiently effective, the PU foam collapses prior to reachingmaximum rise height. If stabilization is excessive, rise of the foam isvery prolonged, and gas pressure in the foam does not reduce. Becausethe cell structure is then very closed, contraction in volume of the gasas it cools causes shrinkage of the foam.

Results of Foaming of Reaction Products of the Above Inventive ExamplesFindings for Example 1 Comparative Example

The foam rises and its gas pressure does not reduce. Instead of this,rise of the foam is prolonged (>3 min). The foam shrinks markedly duringsubsequent cooling. The shrinkage prevents any measurement of physicalproperties.

Findings for Example 2

The foam rises, and gas pressure in the foam reduces after about 2 min,and no alteration occurs in the foam during subsequent cooling.Subsequent measurement gave cell number as 10 cells/cm and porosity as70 mm (measurement of backpressure, by determining the height of a watercolumn generating an equivalent pressure). This shows that the cellstructure is sufficiently fine and open (the term closed foams beingused for a water column of 300 mm or more). The foam has the desiredether foam properties. The foam stabilizer of example 2 is suitable forproduction of this type of foam.

Findings for Example 3

The foam rises, and gas pressure in the foam reduces after about 2 min,and no alteration occurs in the foam during subsequent cooling.Subsequent measurement gave cell number as 10 cells/cm and porosity as70 mm. This shows that the cell structure is sufficiently fine and open.The foam has the desired ether foam properties. The foam stabilizer ofexample 3 is suitable for production of this type of foam.

Having thus described in detail various embodiments of the presentinvention, it is to be understood that the invention defined by theabove paragraphs is not to be limited to particular details set forth inthe above description as many apparent variations thereof are possiblewithout departing from the spirit or scope of the present invention.

1. A process for the preparation of SiOC-linked, linearpolydimethylsiloxane-polyoxyalkylene block copolymers having (AB) repeatunits, which comprises reaction of one or more polyetherdiols with astoichiometric excess of α,ω-dihydropolydimethylsiloxanes and at leastone tertiary amine as catalyst, wherein, after completed reaction of thealcohol component, continuing the reaction in the presence of wateruntil no remaining ≡Si(H) groups are detectable by a gas-volumetricmethod.
 2. The process of claim 1, via reaction of polyorganosiloxaneswhich contain —Si(H) units and which have the general formula (II)where:

where: R, independently of one another, is methyl, and b is from 8 to80, with at least one alcohol selected from the group of thepolyetherdiols with the general formula (III)HO—(C_(n)H_((2n-m))R¹ _(m)O—)_(x)—H  (III) where R¹, independently ofone another, are C₁-C₄-alkyl radicals, n is from 2 to 4, m is 0 or 1,and x has a value from 1 to 200, where the oxyalkylene segments—(C_(n)H_((2n-m))R¹ _(m)O—) can differ from one another within anoxyalkylene ether radical, and the sequence of the individual—(C_(n)H_((2n-m))R¹ _(m)O—) segments are block copolymers, randompolymers, and combinations thereof.
 3. The process of claim 1, whereinat least one tertiary amine is used as catalyst.
 4. The process of claim1, wherein the catalyst used comprises at least one tertiary amineselected from the group consisting of the cycloaliphatic amine bases and1,8-diazabicyclo[5.4.0]undec-7-ene.
 5. The process of claim 1, whereinthe catalyst used comprises at least one tertiary amine selected fromthe group consisting of: pyridines, pyrimidines, pyridazine, pyrazine,quinoline, imidazole, quinuclidine, diazabicyclo[2.2.2]octane, and1,8-diazabicyclo[5.4.0]undec-7-ene.
 6. The process of claim 1, whereinthe average molar mass of each siloxane block (A) (—R₂SiO—)_(b), whereR═CH₃—, is from 650 to about 6000 g/mol.
 7. The process of claim 1,wherein the polyoxyalkylene block (B) contains mixed oxyethylene unitsand oxypropylene units (—C_(n)H_((2n-1))R¹ _(m)O—)_(c) with anoxyethylene content of about 30 to about 70% by weight and oxypropylenecontent of about 70 to about 30% by weight, based on the total contentof oxyalkylene units in the block.
 8. The process of claim 1, whereinthe average molar mass of each polyoxyalkylene block (B)(C_(n)H_((2n-1))R¹ _(m)O)_(c) is from about 600 to about 10 000 g/mol.9. The process of claim 1, wherein the content of the siloxane blocks inthe entire copolymer is from about 20 to about 50% by weight.
 10. Theprocess of claim 1, wherein the number average molar mass Mn of theblock copolymer is from about 10 000 g/mol to about 1 600 000 g/mol. 11.The process of claim 1, wherein the catalyst used is a cycloaliphaticamine base selected from the group consisting of quinuclidine anddiazabicyclo[2.2.2]octane.